Post-translational modifications of recombinant human factor VIII will be determined. Both the "native" and reduced/aldylated "subunits" of factor VIII will be digested withtryptin and analyzed by LC/ESIMS and SIM for carbohydrates, phosphate and sulfate esters. The disulfide bridges will be determined from LC/ESIMS data of the unreduced and tryptic digest. The disulfide-containing peptides will be isolated and subjected to MALDI-TOF analysis before and after reduction.